Indicator lamp control circuit



Jan. 21, 1969 R. WILLIAMS I 3, 5

I INDICATOR LAMP CONTROL CIRCUIT Filed May 13. 1965 'INVENTOR RICHARD WILLIAMS KEVIN c. McMAHON AGENT United States Patent 3,423,745 INDICATOR LAMP CONTROL CIRCUIT Richard Williams, Livonia, Mich., assignor t0 Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed May 13, 1965, Ser. No. 455,497 US. Cl. 340176 Claims Int. Cl. H04q 1/18 ABSTRACT OF THE DISCLOSURE A control circuit for indicating devices which controls the operation of a plurality of parallel connected indicator lamps, each connected in series with selectively operable switches, and a separate normally lighted lamp. All of the lamps are coupled for energization to a single voltage supply. Diode means separately couple the switches to the normally lighted lamp for extinguishing it when any one or more of the parallel connected lamps is lighted.

This invention relates generally to control circuits for indicator lamps and more particularly to circuits for controlling the individual actuation of a plurality of indicating lamps with a lesser number of switches.

The keyboard input to accounting and data processing machines is usually divided into a numerical section and a typewriter section. The numerical section of the keyboard has a plurality of number keys arranged in rows and columns thereon. All the keys in a row are of the same value, and the value of the rows is graduated from 0 to 9. Control keys which determine the operation to be performed with the quantities inserted in the number keys are set to the side of the keyboard.

The order of magnitude of the number inserted into the machine by way of the keyboard is determined by the location of the decimal point. In many machines its position is indicated by decimal indicator lamps set between each two columns. In order that the machine will be able to handle a wide range of numbers, the decimal point is movable from column to column but, of course, only one lamp may be on at a time.

Some previous circuits used to control lamps of this type have required the use of double-pole, single-throw switches and a plurality of equal, independent voltage sources. The circuitry involved is fairly complicated and, because of space and design requirements, impractical in many operations. Other circuits have used solenoid actuated switches having separate sets of contacts for each lamp. These circuits again have the same disadvantages of requiring relatively large amounts of space and complicated circuitry.

It is, therefore, an object of my invention to simplify the circuitry required to control decimal indicating lamps.

A further object of my invention is to provide a control circuit for indicating lamps using a single voltage supply.

A further object of my invention is to provide a circuit for controlling a plurality of indicating lamps using a lesser number of switches in conjunction with a single voltage supply.

In carrying out these and other objects of my invention, I provide a plurality of parallel connected lamps, each connected in series with selectively operable switches, and a separate normally lighted lamp. All of the lamps are coupled for energization to a single voltage supply. Diode means separately couple the selectively operable switches to the normally lighted lamp for extinguishing it when any of the parallel connected lamps is lighted.

Various other objects, advantages and features of my invention will become more fully apparent from the following specification with its appended claims and accompanying drawings in which:

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FIG. 1 is a schematic diagram of a 3-lamp circuit embodying my invention.

FIG. 2 shows a modified 3-lamp circuit embodying my invention.

FIG. 3 is a schematic diagram of a 2-lamp circuit embodying my invention.

My invention can best be understood by referring to the following detailed description of the illustrated embodiments.

Referring to FIG. 1 of the drawings, which illustrates the preferred embodiment of my invention, lamps 11 and 13 are connected in series with normally open single-pole, single-throw switches 15 and 17, respectively. The other terminals of the switches are connected to a point of reference potential such as ground. The other sides of the lamps are connected to voltage source V through resistor 19. One terminal of lamp 21 is connected to a point of reference potential and the other is connected to voltage source V through impedance 23. The junction of lamp 21 and impedance 23 is connected to the junction of switch 15 and lamp 11 through diode 25 and to the junction of switch 17 and lamp 13 through diode 27. These diodes are poled so as to clamp the junction of impedance 23 and lamp 21 at or above the reference potential when either of the switches 15 or 17 is closed.

When both switches are open, lamps 11 and 13 are open circuited and are thus extinguished. Lamp 21 is actuated by current from voltage source -V through resistor 23. When either of the switches 15 or 17 is closed, the lamp with which it is in series, 11 or 13, is lighted by current from voltage source V through resistor 19. The closing of this switch also connects the anode of the diode 25 or 27, respectively, to ground. This clamps the junction of lamp 21 and resistor 23 at ground potential and thereby extinguishes lamp 21 since both its terminals are grounded.

Other types of switches could be used in the 3-lamp embodiment of my invention illustrated in FIG. 1. FIG. 2 illustrates another embodiment of my invention showing the use of a single-pole, double-throw switch 41 in a 3- lamp embodiment of my invention. This circuit operates in exactly the same manner as the circuit in FIG. 1 and corresponding components in the two figures are numbered similarly.

It is also apparent that electronic switching means, such as transistors, may be used if desired in place of the mechanically operated switches illustrated in the drawings.

The circuit shown in FIG. 3 of the drawings is similar to that of FIG. 1 except that it has only one series-con nected lamp-switch combination. Switch 29 and lamp 31 are connected in series. The other terminal of switch 29 is grounded and the other end of lamp 31 is connected to voltage source V through resistor 33. Lamp 35 and resistor 37 are connected in series between ground and voltage source -V. Diode 39 connects the junction of switch 29 and lamp 31 to the junction of lamp 35 and resistor 37.

The circuit operates in the same manner as that shown in FIG. 1. When switch 29 is open, lamp 31 is off and lamp 35 is lighted. When switch 29 is closed, the junction of resistor 37 and lamp 35 is clamped to ground, extinguishing lamp 35. The closing of switch 29 also completes the circuit of lamp 31 and causes it to light.

The two-lamp embodiment of my invention shown in FIG. 3 is particularly useful in binary indicating circuits. A 0 is represented by one configuration of the lamps and a 1 by the opposite configuration.

It is obvious that any number of series combinations of switches and lamps may be connected in parallel witl the two already present in FIG. 1. The junction of the switch and lamp of each is connected to the junction 0: the resistor 23 and lamp 21 through a diode in the same manner as the two combinations present. As long as al the switches are open, lamp 21 is lighted. However, i:

any of the switches are closed, lamp 21 is extinguished and the lamp in series with the closed switch lights. It would also be possible to close a number of switches at the same time, thereby lighting the lamps in series with the closed switches and extinguishing lamp 21.

It is to be understood that the foregoing description is by way of illustration only and, as would be obvious to one skilled in the art, my invention can find many uses in environments other than business machines. It is also obvious that other indicating means, visual or audible, could equally well be used in place of the lamps shown in the drawings.

I claim:

1. An indicating circuit comprising a plurality of two-terminal electrical indicating means,

switch means connected between one terminal of each of all but one of said indicating means and a point of reference potential,

impedance means connecting one terminal of said one indicating means to said reference potential, means for connecting the other terminal of all of said indicating means to a voltage source, and

unidirectional current conducting means for clamping the junction of said impedance means and said one indicating means to said reference potential when at least one of said indicating means is connected to said point of reference potential by said switch means.

2. The device of claim 1 wherein said indicating means comprise indicating lamps and said switch means comprise normally open single-pole, single-throw switches.

3. The device of claim 2 wherein said unidirectional current conducting means comprise semiconductor diodes individually connecting the lamp-connected terminals of the switches to the junction of said impedance means and said one lamp.

4. The device of claim 1 comprising three indicating means and wherein said switch means is a single-pole, double-throw switch.

5. A control circuit for a plurality of indicating lamps comprising normally open single-pole, single-throw switches respectively in series with all but one of said lamps, the other end of said lamps being coupled to a source of voltage and the other end of said switches being connected to a point of reference potential,

resistive means in series with said one of said lamps,

said one lamp and resistive means being connected between a point of reference potential and said source of voltage, and

diode means coupling the lamp-connected terminal of said switches to the junction of said one lamp and said resistive means for clamping said junction of said one lamp and said resistive means to said reference potential when any of said switches is closed.

6. A control circuit for a plurality of indicating lamps comprising switches connected to all but one of said lamps,

continuously acting energizing means connected across said lamps and switches,

resistive means connected in series with said one lamp,

said energizing means being also connected across said resistive means and said one lamp, and

diode means for extinguishing said one lamp when one or more of said switches are closed.

7. The device of claim 6 wherein said switches comprise normally open single-pole, single-throw switches connected in series with each of said lamps.

8. An indicating circuit comprising two indicating lamps,

a single-pole, single-throw switch in series with one of said lamps,

impedance means connected in series with the other of said lamps,

continually acting energizing means for said series combinations, and

diode means connected to the junction of said impedance means and said other lamp for extinguishing said other lamp when said switch is closed. 9. An indicating circuit comprising a plurality of parallel connected electrical indicating means, selectively operable switching means in series with each of said parallel connected indicating means,

separate normally activated electrical indicating means,

and

unidirectional current conducting means separately coupling said parallel connected indicating means to said normally activated indicating means for de-energizing said normally activated indicating means when any of said selectively operable indicating means is activated.

10. An indicating circuit comprising a single-pole, double-throw switch,

two indicating lamps connected between an energizing source and the outer terminals of said switch, the wiper of said switch being connected to a point of reference potential,

a third lamp, said third lamp being normally lighted from said energizing source, and

diode means separately coupling said first two lamps to said third lamp for extinguishing said third lamp when either of said first two lamps is lighted.

References Cited UNITED STATES PATENTS 2,962,703 11 1960 Summerer.

3,271,621 9/1966 McDermott.

JOHN W. CALDWELL, Primary Examiner. D. J. YUSKO, Assistant Examiner.

US. Cl. X.R. 340332, 252 

